US9554429B2 - Lighting circuit, in particular with LED light sources - Google Patents

Lighting circuit, in particular with LED light sources Download PDF

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US9554429B2
US9554429B2 US14/103,984 US201314103984A US9554429B2 US 9554429 B2 US9554429 B2 US 9554429B2 US 201314103984 A US201314103984 A US 201314103984A US 9554429 B2 US9554429 B2 US 9554429B2
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Prior art keywords
circuit
selection
lighting circuit
circuit board
driving current
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US20140159576A1 (en
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Stefano Marchesin
Andrea Englaro
Matteo Iellina
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Marelli Automotive Lighting Italy SpA
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Automotive Lighting Italia SpA
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Assigned to AUTOMOTIVE LIGHTING ITALIA S.P.A. reassignment AUTOMOTIVE LIGHTING ITALIA S.P.A. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: Englaro, Andrea, IELLINA, MATTEO, MARCHESIN, STEFANO
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Assigned to AUTOMOTIVE LIGHTING ITALIA S.P.A. A SOCIO UNICO reassignment AUTOMOTIVE LIGHTING ITALIA S.P.A. A SOCIO UNICO CORRECTIVE ASSIGNMENT TO CORRECT THE ASSIGNEE NAME PREVIOUSLY RECORDED AT REEL: 032255 FRAME: 0746. ASSIGNOR(S) HEREBY CONFIRMS THE ASSIGNMENT. Assignors: Englaro, Andrea, IELLINA, MATTEO, MARCHESIN, STEFANO
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/30—Driver circuits
    • H05B45/37—Converter circuits
    • H05B45/3725—Switched mode power supply [SMPS]
    • H05B33/0815—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60Q—ARRANGEMENT OF SIGNALLING OR LIGHTING DEVICES, THE MOUNTING OR SUPPORTING THEREOF OR CIRCUITS THEREFOR, FOR VEHICLES IN GENERAL
    • B60Q1/00—Arrangement of optical signalling or lighting devices, the mounting or supporting thereof or circuits therefor
    • H05B33/0827—
    • H05B33/0845—
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/40—Details of LED load circuits
    • H05B45/44—Details of LED load circuits with an active control inside an LED matrix
    • H05B45/46—Details of LED load circuits with an active control inside an LED matrix having LEDs disposed in parallel lines

Definitions

  • the present invention relates to a lighting circuit, in particular with LED light sources, for making vehicle lights.
  • LEDs are supplied by manufacturers classified according to their voltage, flow category, or flow selection.
  • voltage selection refers to a voltage range within which the junction voltage characteristic of a category lies, as obtained by supplying the LED with its nominal current.
  • a light source having a certain flow selection means that the source, when driven at nominal voltage, emits a luminous flow variable within a specific and limited predefined range.
  • the LED light sources of the lighting circuit are generally placed on separate electronic lighting circuit boards.
  • the lighting circuit In order for the electronic lighting circuit boards to have the same electric and photometric behaviour throughout the operating range of supply voltages, the lighting circuit must include lighting circuit boards fitting light sources having the same voltage and flow selection. From a practical point of view, this requires connecting the circuit boards mechanically during the SMT soldering process of the electric components to the circuit boards. However, this imposes restrictions and constraints with respect to the relative geometric position of the circuit boards.
  • the circuit boards must be assembled simultaneously and must therefore comply with certain restrictions imposed by the wiring and positioning, restrictions during in-line assembly of the light, and material and process costs (because a selective soldering process must be provided for the mechanical soldering connection of the circuit boards). As a result, there is a need in the art to have greater flexibility in the production of the electronic circuit boards and reduced difficulty in the in-line assembly of the light.
  • a main object of the invention is to permit the realisation of a lighting circuit having light sources with different voltage and flow selections. This is achieved by a lighting circuit, an electronic control circuit board, a lighting circuit board, and a driver method of the present invention.
  • FIG. 1 is a block diagram of the lighting circuit according to the invention.
  • FIG. 2 is a block diagram of the lighting circuit according to the invention, in one embodiment
  • FIG. 3 is a block diagram of a part of the lighting circuit, in another embodiment
  • FIG. 4 is a block diagram of the lighting circuit according to the invention, in a further embodiment
  • FIG. 5 is a block diagram of the lighting circuit in an embodiment variant compared to the circuit in FIG. 4 ;
  • FIG. 6 is a block diagram of the comparator circuit for a driver circuit of lighting circuit boards having different functions.
  • circuit refers both to a direct electrical connection between two circuits or circuit elements and to an indirect connection by one or more active or passive intermediate elements.
  • circuit may indicate either a single component or a plurality of components, active and/or passive, connected to each other to achieve a predefined function.
  • BJT bipolar junction transistor
  • FET field effect transistor
  • base the meaning of the terms “base”, “collector”, and “emitter” include the terms “gate”, “drain”, and “source” (and vice versa).
  • NPN type transistors may be used in place of PNP transistor (and vice versa).
  • the lighting circuit according to the present invention is shown in the block diagram in FIG. 1 .
  • the circuit includes at least two electronic lighting circuit boards 10 , generally but not necessarily separate from each other, each including at least one light source 12 , particularly of the LED type.
  • the electronic lighting circuit boards are controlled by an electronic control unit 100 , which can be mounted on its own electronic control circuit board 110 (as in the example shown) or on one of the electronic lighting circuit boards 10 .
  • the lighting circuit includes a first and a second lighting circuit board 10 . It will however be clear to a person skilled in the art that the invention may be extended to a greater number of electronic lighting circuit boards 10 .
  • the at least one light source 12 of the first lighting circuit board is defined by a first voltage selection and is susceptible to being driven by a first driving current 11 ;
  • the at least one light source 12 of the second lighting circuit board is defined by a second voltage selection and is susceptible to being driven by a second driving current 12 .
  • the idea behind the present invention is to make the electronic control unit 100 detect the value of the voltage selections, identify the higher one, and regulate the current absorbed by the light source defined by the lower voltage selection so that the driving current follows (with a constant ratio) the trend of the driving current absorbed by the light source defined by the higher voltage selection, the latter being taken as reference.
  • the constant ratio is equal to one.
  • the driving current of the lighting circuit board with the lower voltage selection is regulated so as to be equal to the driving current of the lighting circuit board with the higher voltage selection.
  • the current absorbed by the light sources with the lower voltage selection (which would be greater than that of the light sources with the higher selection) is lowered so as to coincide with the latter.
  • the voltage-current characteristics of the lighting circuit boards come to overlap.
  • the circuit according to the invention acts so as to regulate the driving current of the lighting circuit board with the lower voltage selection so that its ratio to the reference current is constant and equal to the K value calculated at the nominal voltage. Consequently, to perform the same function (for example, the same light of a vehicle light), lighting circuit boards coming from panels of different circuit boards may be used that were manufactured at different times and that have different categories and voltage selections.
  • each voltage category varies over a sub-range of 150 mV.
  • the voltage selection 3 A is in a range of 1.9-2.05 V.
  • each electronic lighting circuit board 10 may include, as in the example shown, a respective current driver 20 suitable to impose a driving current of the respective light source 12 (or of the respective light sources, for example in the case of LEDs).
  • each lighting circuit board 10 is provided with a respective selection circuit 14 suitable to identify the value of the respective voltage selection.
  • the electronic control unit 100 detects the voltage selections with the selection circuits 14 .
  • Each selection circuit 14 includes at least one selection circuit element defined by an electric quantity selection having one of a plurality of predefined levels of electric quantity to which the same number of voltage selection levels of the light sources correspond.
  • the circuit selector includes a resistor selection R_SEL having a resistance value chosen from a plurality of predefined resistance values. For example, in the case of four possible voltage selections, each lighting circuit board will mount one out of: a low impedance, high impedance, and two intermediate impedance value resistors, appropriately distanced from each other.
  • Each electronic lighting circuit board may further include a detection circuit 130 , which includes a circuit suitable for detecting a driving electric quantity of the light sources (for example, the driving current), when supplied with a power supply voltage.
  • the electronic control unit 100 may include at least one detection circuit 130 relative to an electronic lighting circuit board 10 .
  • the electronic control unit 100 includes a comparator circuit 120 , consisting of a circuit suitable for comparing the selection electrical quantities, or electrical quantities derivable from the selection electrical quantities, so as to identify (on the basis of the comparison) the lighting circuit board having the at least one light source with the higher voltage selection.
  • a comparator circuit 120 consisting of a circuit suitable for comparing the selection electrical quantities, or electrical quantities derivable from the selection electrical quantities, so as to identify (on the basis of the comparison) the lighting circuit board having the at least one light source with the higher voltage selection.
  • the electronic control unit may further include a regulation circuit 140 consisting of (for each of the electronic lighting circuit boards) a circuit regulator suitable for controlling the respective current driver 20 in such a way that the driving current of the lighting circuit board with the lower voltage selection follows the driving current of the lighting circuit board with the higher voltage selection with a constant ratio.
  • a regulation circuit 140 consisting of (for each of the electronic lighting circuit boards) a circuit regulator suitable for controlling the respective current driver 20 in such a way that the driving current of the lighting circuit board with the lower voltage selection follows the driving current of the lighting circuit board with the higher voltage selection with a constant ratio.
  • at least one electronic lighting circuit board 10 may include the relative circuit regulator so that the regulation circuit 140 is implemented on the electronic lighting circuit board.
  • the comparator circuit 120 is connected to the current driver 20 and to the regulation circuit 140 in such a way that the lighting circuit with the higher voltage selection is driven by the comparator circuit 120 with a reference driving current, and the driving current of the other lighting circuit board is regulated by the respective regulation circuit 140 so as to follow the reference current with a constant ratio.
  • the circuit diagram refers to lighting circuit boards 10 with 12 LEDs including at least one light source of the LED type with a driver type based on the use of a resistor (known as bin resistor) R_BIN_ 1 ; R_BIN_ 2 , suitable to impose a driving current absorbed by the at least one LED.
  • the lighting circuit board diagram is also known as an LED and resistors circuit.
  • the detection circuit 130 detects the driving current and preferably (but not necessarily) uses the bin resistor R_BIN.
  • the detection circuit 130 translates the voltage at the ends of the bin resistor R_BIN_ 1 ; R_BIN_ 2 into a proportional current Is_ 1 ; Is_ 2 . It is to be noted that the detection circuit 130 (here described as belonging to the lighting circuit board 10 ) could also be placed on the control circuit board 110 . In the same way, the regulation circuit 140 may be placed on either the lighting circuit board or the electronic control unit.
  • the detection circuit 130 in one embodiment it may be implemented with the circuit in FIG. 2 .
  • An analysis of the circuit shows that on the terminal Is_ 1 ; Is_ 2 a current Is proportional to the voltage at the ends of the bin resistor R_BIN, and thus to the driving current of the light sources, is present.
  • the electronic control unit 100 it is provided with a circuit suitable to establish which of the lighting circuit boards has the highest voltage selection.
  • a comparator circuit 120 is provided which compares electric quantities correlated to the selection resistors R_SEL of the lighting circuit boards, preferably voltage drops V 1 ; V 2 generated by the resistors. To obtain the voltage drops V 1 ; V 2 to compare, the circuit implementation shown in FIG.
  • the input terminals V_ 1 and V_ 2 of the comparator circuit are at respective voltage values V 1 ; V 2 measured at the ends of the resistors R 15 , R 16 , equal to each other, which form the voltage dividers with the selection resistors RSEL_ 1 and RSEL 2 .
  • the comparator circuit 120 is substantially a differential amplifier which operates as follows: it is assumed that V 1 >V 2 . By appropriately choosing the selection resistors, so that the voltage difference between V 1 and V 2 is such as to bar the transistor Q 1 on the base of which V 2 is present, the voltage VD at the ends of the resistor R 6 is made greater than V 2 and thus the transistor Q 1 is off. This implies that the PNP-type transistor Q 5 , the base of which is connected to the collector of Q 1 , is also barred and no current circulates throughout the branch of the comparator relative to V 2 .
  • the transistor Q 12 (on the base of which V 1 is present) is in saturation or in linear zone (on) and also turns on the PNP-type transistor Q 8 the base of which is connected to the transistor Q 12 .
  • the differential amplifier moves to one side or the other and makes current circulate on only one of the output terminals CTRL_ 1 , CTRL_ 2 .
  • lighting circuit boards with the same voltage selections mount slightly different selection resistors. For example, two lighting circuit boards with 3 A voltage selection will respectively have a resistor of 0 ohm and a resistor of 1 kohm Consequently, the comparator circuit will detect one voltage V 1 or V 2 higher than the other.
  • the output terminals CTRL_ 1 and CTRL- 2 of the comparator circuit are connected to respective transistor emitter terminals Q 6 and Q 2 , the base of which is connected to the output of a respective operational amplifier U 2 , U 1 of the regulation circuit.
  • the regulation circuit illustrated in FIG. 2 thus includes two separate feedback circuits 140 ′, 140 ′′ each based on a respective operational amplifier U 1 , U 2 . These circuits operate in mutual exclusion, in that the respective operational amplifiers U 1 , U 2 have at their respective inverting and non-inverting inputs, the respectively inverted signals feedback 1 and feedback 2 .
  • the regulation circuit includes a driver, such as a driving switch 20 (for example an NPN transistor) for each lighting circuit board.
  • the driver drives a respective driving current on the at least one light source of the LED type of a lighting circuit board, so as to comply with the driving current on at least one light source of the LED type of the other lighting circuit board taken as reference, as is explained further below.
  • Each feedback circuit forms a feedback loop which includes the output terminal of the operational amplifier U 1 ; U 2 , the base of the output transistor Q 2 ; Q 6 , the emitter of the output transistor, and the base of the driving transistor Q 7 ; Q 11 .
  • the lighting circuit according to the invention is made in such a way that the operational amplifier of the regulation circuit, which should regulate the lighting circuit board with the higher voltage selection (which acts as reference) cannot close the feedback.
  • the operational amplifier cannot close the loop to perform a negative feedback and will consequently have one of its outputs CTRL_ 1 or CTRL_ 2 undetermined or not useful for controlling the respective driving transistor.
  • the comparator circuit 120 acts in a complementary manner to the regulation circuit.
  • the side of the comparator circuit which caused the undetermined state of the respective feedback circuit of the regulation circuit has an output suitable to send the driving transistor of the relative lighting circuit board 20 in saturation, thus identifying the circuit board which will act as reference.
  • the output of the comparator circuit (which current does not circulate in) is suitable for controlling the respective feedback circuit so that it is able to close the feedback.
  • the driving circuit 20 is then regulated so that the respective detection circuit provides an output signal which, carried to the input of the respective operational amplifier, closes the feedback loop.
  • the operational amplifier on the basis of its inputs feedback 1 and feedback 2 , provides an output signal suitable to make the inputs equal.
  • the lighting circuit board with the highest selection out of all the possible voltage categories will be a reference circuit board; similarly, the lighting circuit board with the lowest voltage selection out of all the possible voltage categories will be regulated. Consequently, during the step of assembling the lighting circuit boards with the extreme voltage selections (for example 3 A and 4 B for the red LEDs), the assembly of some components may be avoided.
  • the driver for example, the driving switch 20
  • the driving switch 20 since the driving switch 20 will work in saturation, it may be replaced by a simple and economical jumper at 0 ohm.
  • the comparator circuit need not be mounted, in that it is already known which is the circuit board to be regulated, and which is the reference circuit board.
  • the driver of each lighting circuit board is composed of an integrated device, known as an integrated LED driver.
  • the integrated LED driver reads the current which crosses it and compares it to a reference electric quantity which the driver generates internally and which may be voltage or a current.
  • an electric component is connected (for example, a resistor).
  • the LED integrated driver If, for example, the LED integrated driver generates a reference electric current, the current is made to pass through the external setting resistor of the current, and the driver compares the voltage at the ends of the external setting resistor of the current with the voltage detected at the ends of the inner sensing resistor generated by the driver current.
  • the driver thus acts so that these two currents are the same, or in a clearly defined ratio.
  • FIG. 3 is a circuit diagram of an integrated LED driver 200 utilisable in the lighting circuit according to the invention, to which a row of LEDs 12 is connected.
  • the integrated LED driver 200 generates a reference voltage Vs (for example, by a current or voltage generator 210 ).
  • a setting resistor RS is connected to the driver 200 .
  • the driver is able to measure the voltage generated by the driving current I 0 on an inner resistor (for example, by a voltmeter V).
  • each lighting circuit board is provided with a detection circuit of a driving quantity (for example, the current) which supplies a feedback signal feedback 1 ; feedback 2 to the regulation circuit. Further, a comparator circuit is provided which operates in mutual exclusion with the regulation circuit. The operator circuit acts in the same way described above to identify which is the reference lighting circuit board. The method of performing the regulation will now be described.
  • Regulation is achieved by connecting to the integrated LED driver 200 the output of an operational amplifier 220 on the input terminals of which the feedback 1 and feedback 2 feedback signals coming from the two lighting circuit boards 10 are carried. On the output terminal of the operational amplifier, a feedback current IR is present which tends to cancel out the difference between the two feedback signals. Applying Kirchoff's law to the connection node S between the output of the operational amplifier and the integrated LED driver, one has:
  • the control transistor 230 can be controlled by the comparator circuit in such a way that if the transistor is turned on (conducts current) the potential at the output of the operational amplifier and thus the current I R will be equal to zero.
  • the comparator circuit imposes that the control transistor 230 operates as an open circuit.
  • the operational amplifier 220 is thus able to supply the feedback current I R , which tends to cancel out the difference between the feedback signals feedback 1 and feedback 2 coming from the detection circuits of the respective lighting circuit boards. So, the feedback loop closes with the feedback at the input of the operational amplifier. Consequently, the I S current which is that coming out of the integrated LED driver 200 for obtaining the driving current through the constant K, is equal to the I′ S ⁇ I R , with I R >0, given that the regulation is performed.
  • the electronic control unit again includes a comparator circuit 120 ′ which, despite being slightly different from that described above for reasons of convenience of circuit, functions in exactly the same manner to identify the lighting circuit board with the highest voltage selection on the basis of the comparison of the voltages V 1 and V 2 representing the voltage selections.
  • the electronic control unit further includes a regulation circuit which, for each lighting circuit board, is formed of a control stage 140 a ′, 140 a ′′ and of a regulation stage 140 b ′, 140 b ′′.
  • the control stage is connected to the non-inverting input of the operational amplifier 310 which controls the driving transistor 300 , and is controlled by the control stage.
  • the regulation stage includes a regulation transistor 320 (for example of the PNP type) having the emitter connected to a reference voltage VRef, the collector connected to ground by a pull-down resistor R 14 ; R 16 and the base connected to a control terminal C_ 1 ; C_ 2 of the control stage.
  • a regulation transistor 320 for example of the PNP type
  • the control stage is equivalent to the feedback circuit described for the case of LED driving of several resistors in FIG. 1 , that is to say works to close the feedback loop to cancel out the difference between the feedback signal IS_ 1 ; IS_ 2 coming from the respective detection circuits only in the presence of a determined level of control signal C_ 1 ; C_ 2 coming from the comparator circuit.
  • each control signal C_ 1 ; C_ 2 may, depending on the level it assumes, polarise the regulation transistor 320 so that it operates in saturation or in linear zone.
  • the control signal which controls the lighting circuit board which must act a reference will then make the regulation transistor work in saturation, so that the voltage on the non-inverting input of the operational amplifier depends exclusively on the reference voltage VRef according to a predetermined resistance ratio.
  • the control signal which controls the lighting circuit board which must be regulated to conduct a driving current which follows the reference current according to a constant ratio, will then make the regulation transistor 320 work in linear zone, so that the voltage on the non-inverting input of the operational amplifier 310 is proportional to the output of the operational amplifier of the control stage (tends to cancel out the difference between the feedback signals coming from the detection circuits).
  • the above description refers to lighting circuit boards suitable to perform the same function, in particular the same vehicle light (for example, a brake light, side light, reverse light, indicator light, fog light, dipped beam headlight, or full beam headlight).
  • the invention may also be applied to the case in which the lighting circuit boards perform different functions, for example different lights of a vehicle, so that they come on and off in a uniform manner. For example, consider a brake light realised with two LED lighting circuit boards and a side light realised with an LED lighting circuit board. These two lights should function in a uniform manner. Consequently, as described above, the electronic control unit determines the lighting circuit board with the worst voltage selection (the highest) and regulates the current of the other lighting circuit boards.
  • the comparator circuit 400 for lighting circuit boards with different functions is modified as shown in FIG. 6 .
  • the central structure of the comparator is identical to that described above, with the addition of a diagnostic transistor Q 1 ; Q 5 on each branch, connected between the input terminals V_ 1 , V_ 2 of the comparator circuit and ground, and controlled by a respective diagnostic signal DIAG_ 1 ; DIAG_ 2 coming from a respective lighting circuit board.
  • the corresponding branch of the comparator (if it was on and was thus relative to the reference circuit board) goes off. Automatically, the other branch which was off turns on and thus acts as reference. In the presence of a diagnostic signal, the diagnosis transistor conducts and thus the relative branch being in pull-down, the voltage on the input terminal of the branch becomes inferior to the voltage on the input terminal of the other branch. Consequently, the lighting circuit board which functions correctly but initially was not the reference circuit board, does not go off following the failed circuit board going off but becomes the reference circuit board and remains on.
  • the electronic control unit may be implemented in software mode, for example, using a micro controller processing unit or a DSP to make the levels definition and acquisition circuits.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)
US14/103,984 2012-12-12 2013-12-12 Lighting circuit, in particular with LED light sources Active 2034-03-25 US9554429B2 (en)

Applications Claiming Priority (3)

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ITPD2012A0376 2012-12-12
ITPD2012A000376 2012-12-12
IT000376A ITPD20120376A1 (it) 2012-12-12 2012-12-12 Circuito di illuminazione, in particolare con sorgenti luminose a led

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US9554429B2 true US9554429B2 (en) 2017-01-24

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EP (1) EP2744303B1 (it)
CN (1) CN103874286B (it)
ES (1) ES2864770T3 (it)
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DE102017222461A1 (de) * 2016-12-22 2018-06-28 Autosystems America Inc. Konstantstrom-leistungstreiberschaltung für eine automobilleuchtenbaugruppe
JP7101463B2 (ja) * 2017-09-07 2022-07-15 ローム株式会社 発光素子駆動装置、半導体装置、発光装置及び液晶表示装置
TWI641289B (zh) * 2017-09-12 2018-11-11 光寶科技股份有限公司 指示燈裝置及其光源驅動方法
CN110972349B (zh) * 2018-09-27 2021-09-10 Sl株式会社 车辆用灯具的辉度控制装置及方法
CN113727487B (zh) * 2020-10-22 2023-06-23 杰华特微电子股份有限公司 多路led灯串的驱动方法及驱动电路

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CN103874286B (zh) 2019-01-11
ES2864770T3 (es) 2021-10-14
EP2744303A1 (en) 2014-06-18
CN103874286A (zh) 2014-06-18
ITPD20120376A1 (it) 2014-06-13
PL2744303T3 (pl) 2021-09-06
EP2744303B1 (en) 2021-01-27
US20140159576A1 (en) 2014-06-12

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